My Washburn acoustic has a slightly twisted neck.

Replacing the neck is not cost-effective. The guitar sells new for around $225. If you get a new acoustic guitar, take great care to not allow the neck to twist. This is caused by improper truss rod adjustment or temperature and humidty conditions. Never take the guitar from a cold place to a warmer place and get the guitar out or expose it to damp conditions. A guitar should always have some slight relief in the neck but never too much.